The antiblocking system of brakes (ABS) serves for pressure regulation in brake mechanisms of all wheels at braking in difficult road conditions for prevention of blocking of wheels. The system provides:

– A detour of obstacles with higher degree of safety, including at emergency braking;

– Reduction of a brake way at emergency braking with preservation of stability and controllability of the car, including in turn.

In case of malfunction of antiblocking system function of diagnostics and emergency operation of work of system is provided.

The hydroelectronic block of management (ГЭБУ) antiblocking system receives an in-formation about speed and a direction of movement of the car, and also about road conditions from gauges of speed of rotation of wheels.

On the basis of this information the management block defines an optimum mode of braking of wheels.

Fig. 6.48. Elements of antiblocking system of brakes: 1 – the hydroelectronic block of management ABS (ГЭБУ); 2 – the gauge of speed of rotation of a forward wheel; 3 – the gauge of speed of rotation of a back wheel; 4 – control lamp ABS and electronic system of distribution of brake forces; 5 – a diagnostic contact socket

Fig. 6.49. Hydrosystem ABS: 1 – the brake pipeline of the right forward wheel; 2 – the brake pipeline of the left forward wheel; 3 – the brake pipeline of the right back wheel; 4 – the brake pipeline of the left back wheel; 5 – a brake hose of the right forward wheel; 6 – a brake hose of the left forward wheel; 7 – a brake hose of the right back wheel; 8 – a brake hose of the left back wheel; 9 – the hydroelectronic block of management ABS (ГЭБУ); 10 – the vacuum amplifier of brakes and the main brake cylinder

Elements of antiblocking system of brakes are shown on fig. 6.48. The hydrosystem of antiblocking system of brakes is presented on fig. 6.49.

Management ABS

Normal braking. At normal braking the electromagnetic valve is disconnected, the entrance valve is opened, the target valve is closed. By pressing a brake pedal the brake liquid under pressure moves in the wheel cylinder through the electromagnetic valve and puts a brake in action. At отпускании brake pedals the brake liquid comes back in the main brake cylinder through the entrance valve and the return valve.

Operating conditions. If at emergency braking wheel blocking begins, ГЭБУ gives out on the electromagnetic valve a command on reduction of giving of a brake liquid, then pressure moves on each electromagnetic valve. The entrance valve is closed, and giving of a brake liquid in the main cylinder is blocked; the target valve opens, and the brake liquid arrives through the wheel cylinder in a tank that causes pressure decrease.

Mode of maintenance of pressure. At the maximum pressure decrease in wheel cylinder GEBU gives out on the electromagnetic valve a command on maintenance of pressure of a brake liquid, pressure moves on the entrance valve and does not move on the target valve. Thus entrance both target valves are closed also a brake liquid from cylinder wheels ths does not leave.

Mode of increase of pressure. If ГЭБУ defines that the wheel is not blocked, it disconnects the electromagnetic valve. Pressure on electromagnetic valves does not move, the brake liquid through the entrance valve arrives in the wheel cylinder, having given-lenie in which increases.

Electronic system of distribution of brake forces (EBD)

The electronic system of distribution of brake forces (EBD) is subsystem ABS which serves for maintenance of effective coupling of back wheels with a road surface.

Besides, system EBD prevents blocking and drift of back wheels at partial modes of braking.

In the presence of system of distribution of brake forces the brake effort is supported near optimal to value and regulated by electronic system that allows to do without a usual regulator of pressure.

As a pressure regulator – the mechanical device, its possibilities are limited from the point of view of achievement of ideal distribution of brake forces between forward and back wheels, and also flexible distribution of brake forces depending on degree of loading of the car. Besides, malfunction of a mechanical regulator of pressure, as a rule, is not found out by the driver.

The electronic system of distribution of brake forces (EBD) copes the block of management ABS. At movement the system of distribution of brake forces constantly defines

Degree проскальзывания each of wheels of the car also regulates pressure of a working liquid in brake mechanisms of back wheels so that it exceeded pressure in brake mechanisms of forward wheels.

In case of failure detection (tab. 6.1) of system of distribution of brake forces (EBD) in a combination of devices lights up control lamp EBD (and a lay brake).

Table 6.1

Work of systems ABS and ЕВD at detection of malfunctions

Advantages of electronic system of distribution of brake forces is the following.

1. Improvement of work of the basic brake system.

2. Indemnification of a difference of factors of a friction (for each wheel of the car).

3. Absence of necessity for a traditional regulator of pressure.

4. The alarm system about malfunction by means of a control lamp on the panel of devices.

Management of control lamps

Fig. 6.50. Control lamps ABS and EBD

The arrangement of control lamps ABS and EBD in a combination of devices is shown on fig. 6.50.

The module of control lamp ABS. Control lamp ABS shows degree of working capacity ABS.

The control lamp lights up in following cases:

– In a phase of initialization after inclusion of ignition (3);

– In case of an interdiction for action ABS at malfunction;

– If ЭБУ does not join at the included ignition;

– In diagnostics mode.

The module of control lamp EBD. Control lamp EBD shows degree of working capacity EBD.

The control lamp lights up in following cases:

– During a phase of initialization after inclusion of ignition (3);

– In case of an interdiction for action EBD at malfunction;

– If ЭБУ does not join at the included ignition;

– At inclusion of a lay brake or insufficient level of a brake liquid.

THE NOTE

Specified below the phenomenon are not signs of malfunction ABS or EBD.

Features of work of system ABS

Sound at system ABS check. At start-up of the engine from a motor compartment deaf knock is sometimes audible. It is connected with check of working capacity of system.

Sound during action ABS. A sound of work of the electric motor of hydroblock ABS (a howling sound). The scraping sound accompanied by vibration of a pedal of a brake.

During action ABS from the car chassis there are sounds which are caused by repeating cycles of braking and растормаживания wheels (the bumps going from a suspension bracket; a scratch from tyres).

The big brake way. On some road coverings, including on snow-covered roads or гравийном a covering, the brake way of the cars equipped ABS, can be more usual. Therefore at movement on such roads the owner of the car should show care and to move on the lowered speed.

Vibration of a pedal of a brake is the normal phenomenon.

Codes of malfunction ABS are specified in tab. 6.2.

Table 6.2

Codes of malfunctions ABS of brakes

Fig. 6.51. A cable part of a socket of the hydroelectronic block of management ABS

The cable part of a socket of the hydroelectronic block of management ABS is shown on fig. 6.51. Addressing of a cable part of a socket of the hydroelectronic block of management ABS is resulted in tab. 6.3.

Table 6.3

Addressing of contacts of a socket of the hydroelectronic block of management (ГЭБУ) systems ABS

Number

Contact

The address (contact appointment)

The maximum

Current strength

The minimum

Current strength

The note

1

-

-

-

2

-

-

-

3

-

-

-

4

Control lamp EBD

30 мА

5 мА

5

Diagnostics interface

6 мА

3 мА

6

The right forward wheel gauge

16 мА

6 мА

7

The right forward wheel gauge

16 мА

6 мА

8

The right back wheel gauge

16 мА

6 мА

9

-

-

-

10

The left back wheel gauge

16 мА

6 мА

11

The left forward wheel gauge

16 мА

6 мА

12

"Weight"

5-15 AND

2,5 AND

Management ABS

13

Pressure а/б 1 (a food лапанов)

5-15 AND

2 AND

Management ABS

14

Pressure а/б 2 (an electric motor food)

20-39 AND

10 AND

Management ABS

15

"Weight"

20-39 AND

10 AND

Management ABS

16

-

-

-

17

-

-

-

18

-

-

-

19

-

-

-

20

Control lamp ABS

30 мА

5 мА

21

-

22

The switch of a signal of braking

10 мА

5 мА

23

The right back wheel gauge

16 мА

6 мА

24

Ignition

1 AND

500 мА

25

The left back wheel gauge

16 мА

6 мА

26

The left forward wheel gauge

16 мА

6 мА

Removal and installation of elements of antiblocking system of brakes

The hydroelectronic block of management (ГЭБУ) ABS

Removal

Remove the air filter and воздухозаборный a branch pipe.

Fig. 6.52. Contact socket ГЭБУ

Separate contact socket ГЭБУ (fig. 6.52) with a double clamp, having pulled for it upwards.

The moment of an inhaling of bolts of fastening of arm ГЭБУ – 8–10 Н·м.

PREVENTIONS

Dismantling ГЭБУ is not supposed.

Transportation and storage ГЭБУ in vertical position with the muffled apertures is supposed.

Do not merge a liquid from ГЭБУ.

Installation

Installation ГЭБУ spend in an order, the return to removal.

Tighten bolts of fastening ГЭБУ the moment 8–10 Н·м, the union of fastening of the brake I rub-boprovodov the moment 13–17 Н·м.

Check of pressure of a signal of wheel gauges

Establish the car on the lift, switch off a lay brake.

Separate contact socket ГЭБУ and execute check on contacts of a cable part of a contact socket.

THE NOTE

At check remove a double clamp of a contact socket and attach the control device to wires from outside, opposite to socket contacts. Joining measuring щупов the device to contacts does not provide reliable connection

By means of a tester or an oscillograph check up pressure of a signal of wheel gauges, rotating a corresponding wheel with a speed 0,5–1 с–1.

Connection of the control device for check of pressure of a signal of wheel gauges

The wheel gauge of Number of contacts of a socket

The left forward.............. 11, 26

The right forward............ 6, 7

The left back.................. 10, 25

The right back................ 8, 23

Pressure of a signal at measurement by means of an oscillograph, In:

The bottom level..... 0,535 (at a current strength 7 мА)

Top level..... 1,050 (at a current strength 14 мА)

Gauges of speed of rotation of wheels

Fig. 6.54. The gauge of speed of rotation of a forward wheel: 1 – a contact socket of the gauge of speed of rotation of a forward wheel; 2 – the gauge of speed of rotation of a forward wheel

Fig. 6.55. The gauge of speed of rotation of a back wheel: 1 – the gauge of speed of rotation of a back wheel

In a motor compartment separate a contact socket of the forward wheel gauge.

Remove elements of fastening of conducting of the wheel gauge (fig. 6.54 see).

Remove the wheel gauge.

Removal of the back wheel gauge

Separate a contact socket of the back wheel gauge on a wheel nave (fig. 6.55 see).

Remove a brake drum, having turned away the screw of its fastening to a wheel nave.

Turn away four bolts of fastening of a nave of a back wheel to a beam of a back suspension bracket.

Fig. 6.57. Removal of a nave of a back wheel

Remove a nave of a back wheel through the brake mechanism (fig. 6.57).

THE PREVENTION

Do not remove the wheel gauge from a nave hammer blows as it can lead to a gauge exit out of operation.

Removal of air from a hydrodrive of brakes

Operation is spent for effective removal of air from a hydrodrive of brakes and filling with a brake liquid of the hydraulic block of antiblocking system of brakes, brake pipelines and the main brake cylinder.

For removal of air from a hydrodrive of brakes of the cars equipped with antiblocking system, diagnostic device HI-SCAN is used. At carrying out of this operation the device connected to a diagnostic socket under the panel of devices, operates electromagnetic valves and the electric pump

Antiblocking system.

Remove a stopper of a tank of a hydrodrive of brakes and fill a tank with a brake liquid.

For доливки use only brake liquid DOT-3 or DOT-4.

THE PREVENTION

At hit of a brake liquid on a paint and varnish covering of a body immediately смойте its considerable quantity of water.

THE NOTE

At use of special installation for removal of air do not press a brake pedal.

Attach a transparent plastic hose to the prorolling union on wheel tsi-lindre and lower other end of a hose in the transparent capacity half filled with a brake liquid.

Attach device HI-SCAN to the diagnostic socket located under the panel of devices.

By means of device HI-SCAN include the electropump and electromagnetic valves of antiblocking system.

Execute operations as directed, displayed device HI-SCAN.

THE PREVENTION

For prevention перегорания windings of the electric motor of the pump of antiblocking system do not exceed as much as possible admissible time of its work specified on the screen of device HI-SCAN.

Some times press a brake pedal, opening the prorolling union until in a following liquid air vials then tighten the prorolling union will cease to appear.

Execute the described operation on other wheels of the car in a following order: a back right wheel (in a direction of movement of the car), a forward left wheel, a back left wheel, a forward right wheel.